Something bad happened in your dimension, and your Sun pushed you into the portal against your will so you wouldn't get hurt. Everyone else in your dimension ended up getting killed.

You had blacked out right before the portal fully teleported you, but when you woke up, there was someone in front of you. It was Terra, from this new dimension. She looked worried, yet cautious, since she didn't know you.

"Hello? Are you okay? Are you hurt?" She spoke in a surprisingly motherly tone. How could someone be so nice even if they didn't know who you were-?!